1. Field
One embodiment of the invention relates to a printed circuit board having a surface mount device and a through-hole mount device reflow-soldered to a wiring board, and to a method of manufacturing a printed circuit board of this type. The invention further relates to an electronic apparatus having a printed circuit board, such as a portable computer.
2. Description of the Related Art
Printed circuit boards are widely used in electronic apparatuses such as portable computers. A printed circuit board has a wiring board, through-hole mount devices having leads each, and surface mount devices.
The wiring board has a first surface, a second surface that faces away from the first surface. It has through holes that open at both the first surface and the second surface. The inner surface of each through hole is covered with a conductive plated layer. Two lands are formed on the first and second surfaces of the wiring board. One land surrounds the rim of one end of each through hole, and the other land surrounds the rim of the other end of the through hole. Both lands are electrically connected to the plated layer.
Each through-hole mount device has its leads inserted in the through holes. The leads are soldered in the through holes, whereby the through-hole mount device is mounted on the first or second surface of the wiring board. Each surface mount device is placed on one land and then soldered thereto, and is therefore mounted on the first or second surface of the wiring board.
To mount the through-hole mount devices and surface mount devices in high density on the wiring board, it is desirable to arrange them with the through holes located between them. In order to arrange them so, the surface mount devices are soldered to the lands that faces away from the through-hole devices, as is disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 10-41605.
As described in Publication No. 10-41605, the leads of the through-hole device pass through the holes and project from the second surface of the wiring board if the through-hole devices are mounted on the first surface of the wiring board. The distal ends of the leads are covered with solder fillets that flare toward the through holes. The circumferential edge of each solder fillet extends over one land.
Consequently, each surface mount device may interfere with the distal ends of the leads or the solder fillet when it is soldered to a land provided on the second surface of the wiring board. To prevent this interference, the diameter of the land must be increased to displace the surface mount device from the through holes along the diameter thereof. Inevitably, the surface mount device moves from the through hole. A large space should be provided around the through hole, so that the surface mount device may be arranged in it. This makes it difficult to arrange the through-hole mount devices and surface mount devices in high density on the wiring board.